Niners special-teams standout Demarcus Dobbswas ruled out of Sunday's game in St. Louis after he was involved in a single-car accident and subsequently arrested for marijuana possession early Friday morning in Santa Clara, CSN Bay Area reported.

Dobbs, who turned 25 Friday, was also believed to be under the influence of alcohol. He was the only person in the car and was not injured after he crashed on southbound San Tomas Expressway at 3:45 a.m. He was released early Friday morning and faces misdemeanor charges.

The team released a statement: "The 49ers are aware of the recent matter involving Demarcus Dobbs. We are gathering the relevant facts as it pertains to this situation. We have been in contact with both Demarcus and the League office. He will not be making the trip to St. Louis, and we will reserve further comment at this time."

Dobbs, who has three special-teams tackles, leads the team with 567 special-teams points, according to a grading system used by the coaching staff. A backup defensive end, Dobbs also earned a role as the team's No. 4 tight end after an impressive performance on offense during training camp. He made the 53-man roster last year as an undrafted rookie.

On Friday, the 49ers promoted linebacker Michael Wilhoitefrom the practice squad to the 53-man roster. Wilhoite said he will be active Sunday and play on special teams.

Hoping to return: The 49ers' top two nose guards have something in common beyond their position: Both starter Isaac Sopoagaand Ricky Jean Francoiswill become free agents after the season.

Jean Francois, a seventh-round pick in 2009, wants to assume a full-time role after making three starts in three-plus seasons in San Francisco.

In Jean Francois' three starts, all since 2011, the 49ers' run defense has allowed an average of 61 yards a game and 3.3 yards per carry. Defensive coordinator Vic Fangiohas said there isn't a dramatic difference between Jean Francois and Sopoaga.

There could, however, be a difference once they hit the free-agent market: Jean Francois, 26, is younger and figures to be cheaper than Sopoaga, 31. Jean Francois is earning a base salary of $615,000 this season while Sopoaga is earning $3.8 million.

Sopoaga has played 215 snaps this season, 95 more than Jean Francois.

Injury news: Rams wide receiver Danny Amendola(foot), who had 11 catches for 102 yards in a 24-24 tie against the 49ers on Nov. 11, is listed as doubtful for Sunday's game. Amendola played just nine snaps last week in a win against the Cardinals because of the injury and has been in a walking boot this week.

St. Louis defensive end Robert Quinn(8.5 sacks) is questionable because of a concussion. San Francisco's Darcel McBath, a core player on special teams, is also questionable after he sustained a concussion in last week's win against the Saints.

Briefly: Jim Harbaughsaid wide receiver Ted Ginn Jr. will replace Kyle Williamsas the team's emergency quarterback. Williams is out for the season with a torn ACL. ... Punter Andy Lee or nose guard Sopoaga would replace kicker David Akersin the event of injury, Harbaugh said. Akers (pelvis) is probable for Sunday's game.